JP2001057459A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture easily at high precision with less processes, while suppressing a leak current. SOLUTION: On an n-type GaAs substrate 10, an n-type AlGaAs clad layer 12, a GaAs/AlGaAs multiple quantum well active layer 14, a p-type AlGaAs clad layer 16, and a p-type GaAs cap layer 18 are sequentially laminated. With the p-type AlGaAs clad layer 16 etched and removed halfway, an n-type AlGaAs current block layer 20 is formed on both sides of a stripe-like current injection region as well as near the end surface of a resonator. A p-type GaAs contact layer 22 is formed over the entire surface of the p-type GaAs cap layer 18 and an n-type current block layer 20, and a p-side electrode 24 is formed on its surface while forming an n-side electrode 26 on the rear surface side of the n-type GaAs substrate 10. The GaAs/AlGaAs multiple quantum well active layer 14 below the n-type current block layer 20 is an AlGaAs mixed crystal 28 wherein a periodic structure is out of order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly, to a structure of a semiconductor laser having a window structure, for example, a semiconductor laser applicable to an optical disk device, a laser printer, and the like. .

[0002]

2. Description of the Related Art Semiconductor lasers used in recent optical disk devices and the like are required to have higher output. For this reason, in order to increase the output of the semiconductor laser, the injection current is gradually increased, and when a certain optical output is reached, optical damage (hereinafter referred to as COD) of the cavity facet occurs and the optical output sharply decreases. Since it occurs, it was difficult to further increase the output.

Therefore, as a means for avoiding this, a window structure has been developed in which the forbidden band width of the active layer near the end face of the resonator is made larger than that inside. Examples of this type of semiconductor laser include, for example, JP-A-9-275241 and JP-A-10-275241.
There is one described in Japanese Patent No. 290043.

FIG. 8 is a perspective view of a conventional semiconductor laser having a window structure. The semiconductor laser shown in FIG. 8 includes an n-type GaAs substrate 100, an n-type AlGaInP cladding layer 102, a GaInP active layer 104, and a p-type AlGaIn
The P cladding layer 106 and the p-type GaAs contact layer 108 were grown in this order by metal organic chemical vapor deposition.

A ridge is formed by etching using SiO ₂ as a mask, and n-type GaAs for current confinement is formed.
The ridge is buried by selectively growing 110. Then, p-type GaAs near the resonator end face is used.
A ZnSe layer is grown at 450 ° C. on the contact layer 108 to form a Zn diffusion region 116.
On the p-type GaAs contact layer 108, Ti
A p-side electrode 112 made of / Pt / Au is formed, and under the n-type GaAs substrate 100, Au / Ge / Ni / Au
An n-side electrode 114 is formed.

In the case of GaInP or AlGaInP described above, when ordinary crystal growth is carried out using metal organic chemical vapor deposition, Ga and In have an ordered structure (natural superlattice) on the group III sublattice during crystal growth. It is known to form In the case of the above conventional example, a ZnSe layer is grown near the resonator end face to diffuse Zn (Zn diffusion region 116), and the Zn
In the GaInP active layer in which is diffused, the natural superlattice structure is disordered and the band gap is increased. Therefore, a window structure is formed, and the temperature for further diffusion is 450
Due to the low temperature, the deterioration of the crystallinity of the active layer due to heat was suppressed.

FIGS. 9A and 9B show the structure of another conventional semiconductor laser having a window structure. FIG. 9A is a perspective view of the semiconductor laser, and FIG. 9B is a sectional view taken along line AA '. (C) is a sectional view taken along line BB ′. The semiconductor laser in FIG. 9 has an n-Al
GaInP lower cladding layer 120 and MQW active layer 122
P-AlGaInP first upper cladding layer 124;
-GaInP etching stopper layer 126 and p-Al
GaInP second upper cladding layer 128 and p-GaInP
A laminated structure including the band discontinuous relaxation layer 130 was provided. On both sides of the p-AlGaInP second upper cladding layer 128 on the p-GaInP etching stopper layer 126, an n-GaAs current block layer 132 is formed so that the driving current is concentrated on a predetermined band-shaped region constituting the optical waveguide. ing. A p-GaAs contact layer 134 is formed on the entire surface of the p-GaInP band discontinuous relaxation layer 130 and the n-GaAs current blocking layer 132.

[0008] Further, as shown in FIG.
A front surface electrode 140 is formed on the As contact layer 134, and a back surface electrode 14 is formed on the back side of the n-GaAs substrate 118.
2 are formed. Further, Zn diffusion regions 136 are formed at both ends of the optical waveguide, and Zn diffused M
The QW active layer 122 has a disordered periodic structure and is a mixed crystal. Since the band gap of the disordered mixed crystal is larger than that of the original MQW, a window structure is formed. Further, a high resistance region 138 having a size larger than that of the Zn diffusion region 136 is provided in a portion of the n-GaAs current block layer 132 located on the Zn diffusion region 136 by ion implantation. Therefore, since the p-GaAs contact layer 134 is not in direct contact with the Zn diffusion region 136, the leakage current is suppressed.

[0009]

However, in the above-described conventional semiconductor laser, for example, in the case of FIG. 8, the p-side electrode 112 is in contact with the low-resistance Zn diffusion region 116 near the cavity facet. Therefore, there is a problem that a leak current that does not contribute to laser oscillation is likely to occur.

In the case of a semiconductor laser having a window structure as shown in FIG. 9, it is important to reduce leakage current in the window structure, and in order to reduce the leakage current, a high resistance region 138 is formed. Had formed. However, in the manufacturing process of the semiconductor laser shown in FIG.
Patterning to form 36, high resistance region 138
Since at least three photolithography steps of ion implantation mask patterning for forming a mask and etching mask patterning for forming an optical waveguide are required, the number of steps is increased, and misalignment is likely to occur. Therefore, it has been difficult to reduce the leakage current of the semiconductor laser and to easily and accurately produce the semiconductor laser.

The present invention has been made in view of the above, and provides a semiconductor laser having a window structure that can be manufactured easily with high accuracy in a small number of steps and that can suppress leakage current. It is intended to be.

[0012]

According to a first aspect of the present invention, there is provided a semiconductor laser including at least a first conductivity type cladding layer and a superlattice structure on a first conductivity type semiconductor substrate. A laminated structure including an active layer and a cladding layer of the second conductivity type is formed, and a current block layer made of a material having a larger band gap than the active layer is formed on both outer sides of the stripe region and near the resonator end face. The superlattice structure of the active layer located below the current blocking layer is disordered.

According to this, a current block layer is formed near the resonator end face as well as on both outer sides of the stripe-shaped current injection region. For this reason, no current flows near the cavity end face, so that a leak current that does not contribute to laser oscillation can be reduced. Further, the current blocking layer is made of a material having a larger forbidden band width than the active layer. Therefore, the light emitted from the active layer is not absorbed in the vicinity of the cavity end face and on both sides of the stripe-shaped current injection region, and the external quantum efficiency of the laser can be improved. Further, the superlattice structure of the active layer located below the current blocking layer is disordered. For this reason, the forbidden band width of the active layer near the end face of the resonator becomes larger than that of the inside thereof, thereby forming a window structure. At the same time, by disordering the superlattice structure of the active layer on both sides of the stripe-shaped current injection region, the refractive index becomes lower than that of the non-disordered active layer. in this way,
Since the optical waveguide structure is formed by the actual refractive index difference in the horizontal and horizontal directions, the horizontal and horizontal modes are stabilized in a single mode.

According to a second aspect of the present invention, there is provided a semiconductor laser having at least a first conductivity type cladding layer, an active layer having a superlattice structure, a second conductivity type cladding layer, A mesa stripe structure is formed by etching both sides of the stripe region of the second conductivity type cladding layer and the vicinity of the cavity end face, and is more forbidden than the active layer embedded in both sides of the mesa stripe structure and the vicinity of the cavity end face. A stacked structure including a first conductivity type current blocking layer made of a material having a large band width, and a second conductivity type contact layer formed on the second conductivity type cladding layer and the first conductivity type current blocking layer is formed. The superlattice structure of the active layer located below the first conductivity type current blocking layer is disordered.

According to this, in order to form a current confinement structure, both sides of the stripe region of the second conductivity type cladding layer and the vicinity of the cavity end face are mesa-etched. Then, the superlattice structure of the active layer in a region not covered with the mask used for etching is changed by impurity diffusion, ion implantation, Ga
It is disordered by methods such as introduction of vacancies. In addition, a first conductivity type current blocking layer is buried in the mesa-etched region by selective growth using a mask. Therefore, the stripe-shaped current confinement structure, the current confinement structure near the cavity end face, the optical waveguide structure, and the window structure can be formed by one pattern formation, so that the semiconductor laser can be easily manufactured with a small number of manufacturing steps. It can be formed.

According to a third aspect of the present invention, there is provided a semiconductor laser, comprising: a first conductive type clad layer, an active layer having a superlattice structure, a second conductive type clad layer; A mesa stripe structure is formed by etching both sides of the stripe-shaped region of the second conductivity type cladding layer and the vicinity of the resonator end face. A high-concentration Zn doping layer made of a material having a large forbidden band width and a first conductivity type current blocking layer are buried, and a second conductivity type formed on the second conductivity type cladding layer and the first conductivity type current blocking layer. A stacked structure including a contact layer and a superlattice structure of the active layer located under the high-concentration Zn-doped layer is characterized in that Zn is diffused and disordered. .

According to this, a high-concentration Zn-doped layer is formed on both outer sides of the mesa stripe structure and near the resonator end face. Since Zn has a large diffusion coefficient, Zn in the high-concentration Zn-doped layer diffuses to the active layer during the crystal growth of the first conductivity type current blocking layer and the second conductivity type contact layer. For this reason, the superlattice structure of the active layer located under the current blocking layer is disordered, and an optical waveguide structure and a window structure are formed. The laser device of the present invention can be manufactured more easily because a disordering step and an annealing step different from crystal growth are not required to disorder the active layer.

According to a fourth aspect of the present invention, there is provided a semiconductor laser comprising: a first conductive type clad layer, an active layer including a superlattice structure, and a first second conductive type clad layer on a first conductive type semiconductor substrate. And a high-concentration Zn-doped layer made of a material having a larger forbidden band width than the active layer and a first-conductivity-type current blocking layer are laminated, and the high-concentration Zn-doped layer and the first The one conductivity type current block layer is etched to form a groove, and the second second conductivity type is formed on the first second conductivity type clad layer and the first conductivity type current block layer exposed by the etching. The superlattice structure of the active layer under the high-concentration Zn-doped layer in which the clad layer is formed is one in which Zn is diffused and disordered.

According to this, a high concentration Zn doping layer is formed on the first second conductivity type cladding layer. Then, the high-density Z
After etching the n-doped layer to form a groove, when growing the second second-conductivity-type cladding layer, Zn in the high-concentration Zn-doped layer is diffused to disorder the superlattice structure of the active layer. ing. In this structure, the number of crystal growth steps is only two, and the number of crystal growth steps can be reduced by one compared with the structure of the third aspect. Therefore, the structure can be manufactured more easily.

Further, a semiconductor laser according to claim 5 is
2. The semiconductor laser according to claim 1, wherein said current blocking layer is made of a group II-VI compound semiconductor containing Zn.

According to this, the current blocking layer is made of a II-VI group compound semiconductor containing Zn. As a material for the cladding layer, an AlGaAs-based or AlGaInP-based
When a group II-V compound semiconductor is used, band discontinuity increases in both materials, so that it becomes difficult for current to flow. Furthermore,
By controlling the acceptor concentration of the II-VI compound semiconductor containing Zn, high resistance can be obtained. For this reason, it is possible to form an effective current confinement structure. Further, Zn in the current block layer is diffused during crystal growth of the second conductivity type clad layer formed thereafter,
Disorder the superlattice structure of the active layer. Therefore, the optical waveguide structure and the window structure can be easily formed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the semiconductor laser according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment 1) FIG. 1A is a perspective view of a semiconductor laser according to Embodiment 1, FIG. 1B is a sectional view taken along line AA ′ of FIG. 1A, and FIG. Is BB 'of (a)
It is a line sectional view. As shown in FIG. 1, a semiconductor laser according to the first embodiment includes an n-type AlGaAs cladding layer 12, a GaAs / AlGaAs
A multiple quantum well active layer 14, a p-type AlGaAs cladding layer 16, and a p-type GaAs cap layer 18 are sequentially stacked.

The p-type AlGaAs cladding layer 16
Is removed by etching to the middle of the n-type AlGa on both sides of the stripe-shaped current injection region and near the resonator end face.
An As current blocking layer 20 is formed. Further, the p-type GaAs cap layer 18 and the n-type current block layer 20
A p-type GaAs contact layer 22 is formed on the entire upper surface.

Further, a p-side electrode 24 is formed on the surface of the p-type GaAs contact layer 22, and the n-type GaAs substrate 10
The n-side electrode 26 is formed on the back side of the. And n
The multi-quantum well active layer 14 located below the type current block layer 20 has a periodic structure that is disordered.
It is an lGaAs mixed crystal 28.

Hereinafter, the manufacturing process of the semiconductor laser will be described with reference to FIG. 2A to 2E are views showing the manufacturing process of the semiconductor laser shown in FIG. 1, wherein FIGS. 2A to 2E are manufacturing process diagrams viewed from a cross section taken along line AA ′ of FIG. 1, and FIGS. BB in FIG.
It is a manufacturing process figure seen from the 線 line cross section.

First, as shown in FIGS. 2A and 2F, an n-type AlGaAs cladding layer 12, a GaAs / AlGaAs multiple quantum well active layer 14, and a p-type AlGaAs cladding layer are formed on an n-type GaAs substrate 10. 16, p-type GaAs
The s cap layer 18 is epitaxially grown in order. Here, a metal organic chemical vapor deposition method is used as the crystal growth method.

Next, SiN is deposited on the surface of the laminated structure, and rectangular Si is formed by using a photolithography technique.
An N mask 30 is formed. The mask width here is 5
μm, and a SiN mask 30
Not covered with. Then, the semiconductor laminated structure that is not covered with the SiN mask 30 is removed by chemical etching to a part of the p-type AlGaAs cladding layer, whereby the structure shown in FIG.
A mesa structure as shown in (b) and (g) is formed.

Next, a SiO ₂ layer 3 is formed on the entire surface of the laminated structure.
2 and heat treatment is performed. SiO ₂ layer 32 is p
In the region directly in contact with the AlGaAs cladding layer 16, Ga is absorbed by the SiO ₂ layer 32 to form Ga vacancies, and the vacancies are diffused by the heat treatment so that the GaAs / AlGaAs multiplex is formed. Quantum well active layer 14
Is mixed and Al is mixed as shown in FIGS. 2 (c) and 2 (h).
A GaAs mixed crystal 28 is formed.

Next, after removing the SiO ₂ layer 32 with hydrofluoric acid, using the SiN mask 30 as a mask, FIG.
As shown in (i), the n-type AlGaAs current block layer 20 is buried by selective growth.

Thereafter, the SiN mask 30 is removed by dry etching, and a p-type GaAs contact layer 22 is epitaxially grown on the entire surface of the laminated structure. And FIG.
As shown in (e) and (j), a p-side electrode 24 made of AuZn / Au is formed on the surface of the p-type GaAs contact layer 22.
And AuGe / Ni on the back surface of the n-type GaAs substrate 10.
/ Au is formed by vapor deposition of an n-side electrode 26.

In the semiconductor laser manufactured by the above-described steps, the n-type AlGaAs layer current block layers 20 are embedded on both sides of the mesa structure, and the semiconductor laser has a pnpn structure and no current flows. Therefore, the current is concentrated on the mesa portion having a width of 5 μm to reduce the threshold current.

The n-type AlGaAs current blocking layer 2
The GaAs / AlGaAs multiple quantum well active layer 14 located below 0 is an AlGaAs mixed crystal 28. A
The refractive index of the lGaAs mixed crystal 28 is Ga
It is lower than the As / AlGaAs multiple quantum well active layer 14, and a real refractive index difference occurs in the horizontal and horizontal directions. Therefore, an optical waveguide structure is formed, and the horizontal transverse mode is stabilized.

On the other hand, GaAs is also formed near the resonator end face.
/ AlGaAs multiple quantum well active layer 14 is mixed crystal. The forbidden band width of the AlGaAs mixed crystal 28 depends on the GaAs / AlGaAs multiple quantum well active layer 14 which is not mixed.
And constitutes a window structure. Therefore, generation of COD can be suppressed. Also,
N-type AlGaAs current blocking layer 2 also near the cavity end face
Since 0 is embedded, a leakage current that does not contribute to laser oscillation in the window structure can be reduced.

The n-type AlGaAs current blocking layer 2
0 is a GaAs / AlGaAs multiple quantum well active layer 14
The bandgap is larger than that. Therefore, the light emitted from the active layer is not absorbed near the cavity end face or on both side faces of the mesa structure, and the external quantum efficiency of the laser can be improved.

As described with reference to FIG. 2, in the above-described semiconductor laser, the photolithography process is performed only once for forming the pattern of the SiN layer. The SiN mask 30 is formed on the GaAs / AlGaAs multiple quantum well active layer 1.
4 and a mask for selective burying growth of the n-type AlGaAs current blocking layer 20. Accordingly, a stripe-shaped current confinement structure, a current confinement structure near the cavity end face, an optical waveguide structure, and a window structure can be formed by one pattern formation. Therefore, the number of steps is reduced, and the device can be easily manufactured.

In the first embodiment, the GaAs /
As a method of crystallizing the AlGaAs multiple quantum well active layer 14, the introduction of Ga vacancies is used, but the method is not limited to this, and other methods such as Zn diffusion and ion implantation may be used. It is also possible to carry out using.

(Embodiment 2) FIG. 3 shows Embodiment 2 of the present invention.
3A is a perspective view of the semiconductor laser, FIG. 3B is a cross-sectional view taken along line AA ′ of FIG. 3A, and FIG. 3C is a cross-sectional view taken along line BB ′ of FIG. It is sectional drawing.

As shown in FIG. 3, a semiconductor laser according to the second embodiment has an n-type GaAs substrate 10 on which an n-type Al
GaInP cladding layer 40, GaInP active layer 42, p
An AlGaInP cladding layer 44 and a p-type GaInP band discontinuous relaxation layer 46 are sequentially stacked. And p
A mesa stripe structure is formed by etching to a point in the middle of the AlGaInP cladding layer 44 to form a mesa stripe structure.
An n-type AlGaInP current blocking layer 50 made of a material having a larger bandgap than the aInP active layer 42 or a high-concentration Zn
The doped AlGaInP layer 48 is embedded.

The p-type GaAs contact layer 22 is formed on the entire surface of the n-type AlGaInP current blocking layer 50 and the p-type GaInP band discontinuous relaxation layer 46. Further, p-type GaAs contact layer 22 has
A side electrode 24 is formed, and an n-side electrode 26 is formed on the back surface of the n-type GaAs substrate 10. And n-type AlG
GaIn located under aInP current block layer 50
The P active layer 42 is disordered by Zn diffusion to form a Zn diffusion region 52.

Hereinafter, a manufacturing process of the semiconductor laser will be described with reference to FIG. 4A to 4D are views showing a manufacturing process of the semiconductor laser of FIG. 3, wherein FIGS. 4A to 4D are manufacturing process diagrams viewed from a cross section taken along line AA ′ of FIG. 3, and FIGS. BB in FIG.
It is a manufacturing process figure seen from the 線 line cross section.

First, as shown in FIGS. 4A and 4E, an n-type AlGaInP cladding layer 40, a GaInP active layer 42, and a p-type AlGaI
The nP cladding layer 44 and the p-type GaInP band discontinuous relaxation layer 46 are epitaxially grown in this order. Here, a metal organic chemical vapor deposition method is used as the crystal growth method.

Next, SiN is deposited on the surface of the laminated structure, and a rectangular Si
An N mask 30 is formed. The mask width here is 5
μm, and the vicinity of the cavity end face of the semiconductor laser is not covered with the SiN mask 30. Then, this SiN mask 3
4 is removed by chemical etching up to immediately above the GaInP active layer 40, and the semiconductor stacked structure not covered with the GaInP active layer 40 is removed as shown in FIG.
A mesa stripe structure as shown in FIG.

Next, as shown in FIGS. 4 (c) and 4 (g), a high density Z is formed in a region not covered with the SiN mask 30.
n-doped AlGaInP layer 48 and n-type AlGaI
The nP current blocking layer 50 is selectively grown and buried.

Thereafter, the SiN mask 30 is removed by dry etching, and a p-type GaAs contact layer 22 is epitaxially grown on the entire surface of the laminated structure. At this time, Zn in the high-concentration Zn-doped AlGaInP layer 48 becomes active layer 4
Heat treatment is performed so as to diffuse up to 2. And FIG.
As shown in (d) and (h), a p-side electrode 24 made of AuZn / Au is formed on the surface of the p-type GaAs contact layer 22.
And AuGe / Ni on the back surface of the n-type GaAs substrate 10.
/ Au is formed by vapor deposition of an n-side electrode 26.

In the semiconductor laser manufactured by the above steps, the GaInP active layer 42 located under the high concentration Zn-doped AlGaInP layer 48 has a disordered GaInP natural superlattice structure due to the diffusion of Zn. The forbidden band has become larger. Therefore, a difference occurs in the refractive index of the GaInP active layer between the inside and the outside of the mesa stripe structure, and an optical waveguide structure is formed. Therefore, the horizontal and horizontal modes are stabilized in the single mode.

On the other hand, since the disordered GaInP active layer 42 near the cavity facet forms a window structure, generation of COD is suppressed. Since the n-type AlGaInP current blocking layer 50 is buried also in the vicinity of the cavity end face, it is possible to reduce a leak current that does not contribute to laser oscillation in the window structure. GaIn
When the P active layer 42 is disordered, a diffusion step and an annealing step different from the crystal growth are not used.
The process is further simplified as compared with the manufacturing process shown in FIG.

(Embodiment 3) FIG. 5 shows Embodiment 3 of the present invention.
3A is a perspective view of the semiconductor laser, FIG. 3B is a cross-sectional view taken along line AA ′ of FIG. 3A, and FIG. 3C is a cross-sectional view taken along line BB ′ of FIG. It is sectional drawing.

As shown in FIG. 5, a semiconductor laser according to the third embodiment has an n-type GaAs substrate 10 on which an n-type Al
GaInP cladding layer 40, GaInP active layer 42, p
A first AlGaInP cladding layer 60, a high-concentration Zn-doped AlGaInP layer 48, and an n-type AlGaInP current block layer 50 are sequentially stacked. And p-type Al
The first cladding layer 60 of GaInP is removed by chemical etching to form a groove 61, and the entire surface is p-type AlGaI.
The nP second cladding layer 62, the p-type GaInP band discontinuous relaxation layer 46, and the p-type GaAs contact layer 22 are sequentially buried. Further, a p-side electrode 24 is formed on the surface of the p-type GaAs contact layer 22, and the n-type GaAs substrate 10
The n-side electrode 26 is formed on the back surface of the. Then, Zn in the high concentration Zn-doped AlGaInP layer 48 is replaced with GaIn.
By diffusing to the P active layer 42, the natural superlattice structure is disordered to form the Zn diffusion region 52.

Hereinafter, the manufacturing process of the semiconductor laser will be described with reference to FIG. 6A to 6C are diagrams showing a manufacturing process of the semiconductor laser of FIG. 5, wherein FIGS. 6A to 6C are manufacturing process diagrams viewed from a cross section taken along line AA ′ of FIG. 5, and FIGS. BB in FIG.
It is a manufacturing process figure seen from the 線 line cross section.

First, as shown in FIGS. 6A and 6D, an n-type AlGaInP cladding layer 40, a GaInP active layer 42, and a p-type AlGaI
nP first cladding layer 60, high concentration Zn-doped AlGa
InP layer 48, n-type AlGaInP current block layer 50
Are sequentially epitaxially grown. Here, a metal organic chemical vapor deposition method is used as the crystal growth method.

Next, SiN is deposited on the surface of the laminated structure, and a rectangular Si
An N mask 30 is formed. The SiN mask 30 is etched into a stripe having a width of 5 μm to form a window, and the vicinity of the cavity facet of the semiconductor laser is also used in the SiN mask 30.
Covered with. Then, the semiconductor laminated structure not covered with the SiN mask 30 is replaced with a p-type AlGaInP first
The grooves 61 shown in FIGS. 6B and 6E are formed by removing the cladding layer 60 by chemical etching.

Next, the SiN mask 30 is removed by dry etching, and a p-type AlGaInP
The second cladding layer 62, the p-type GaInP band discontinuous relaxation layer 46, and the p-type GaAs contact layer 22 are epitaxially grown in this order. At this time, high concentration Zn
Heat treatment is performed so that Zn in the doped AlGaInP layer 48 diffuses to the GaInP active layer 42. And
As shown in FIGS. 6C and 6F, a p-side electrode 2 made of AuZn / Au is formed on the surface of the p-type GaAs contact layer 22.
4 and AuGe / N on the back surface of the n-type GaAs substrate 10.
An n-side electrode 26 made of i / Au is formed by vapor deposition.

In the semiconductor laser manufactured by the above steps, the n-type AlGaInP layers 50 are formed on both side surfaces of the groove 61, so that the semiconductor laser has a pnpn structure and no current flows. Therefore, the current is concentrated on the groove 61 having a width of 5 μm to reduce the threshold current. Also, a high concentration Zn-doped AlGaIn under the n-type AlGaAs current blocking layer 50 is used.
Zn in the P layer 48 diffuses to the GaInP active layer 42 to disorder the natural superlattice structure.

The refractive index of the disordered GaInP is lower than that of the GaInP active layer 42 in which the natural superlattice structure is formed, and a difference in the actual refractive index occurs in the horizontal and horizontal directions. Therefore, an optical waveguide structure is formed, and the horizontal transverse mode is stabilized.

On the other hand, GaIn also near the resonator end face.
The natural superlattice structure of the P active layer 42 is disordered, and the forbidden band width is increased, forming a window structure. Therefore, generation of COD can be suppressed. Further, the n-type AlGaInP current blocking layer 50 formed near the cavity facet suppresses generation of a leak current that does not contribute to laser oscillation in the window structure.

The n-type AlGaInP current blocking layer 50 has a larger forbidden band width than the GaInP active layer 42. Therefore, the light emitted from the active layer is not absorbed in the vicinity of the cavity end face or on both side faces of the groove 61, and the external quantum efficiency of the semiconductor laser can be improved.

Further, in the manufacturing process described with reference to FIG. 6, the crystal growth process is performed twice, and FIG.
As compared with the manufacturing process described in the above, the number of crystal growth steps can be reduced by one. For this reason, the semiconductor laser can be manufactured more easily with a smaller number of steps.

(Embodiment 4) FIG. 7 shows Embodiment 4 of the present invention.
3A is a perspective view of the semiconductor laser, FIG. 3B is a cross-sectional view taken along line AA ′ of FIG. 3A, and FIG. 3C is a cross-sectional view taken along line BB ′ of FIG. It is sectional drawing. Also,
The manufacturing process of the semiconductor laser of FIG. 7 is substantially the same as that of FIG.

A feature of the fourth embodiment is that ZnSSe lattice-matched to a GaAs substrate is used as a current blocking layer. This ZnSSe is a II-VI group compound semiconductor, and has p-type AlGaInP
The cladding layers 60 and 62 are III-V group compound semiconductors. The bandgap of ZnSSe is larger than that of AlGaInP, and large band discontinuity occurs at the junction interface. Therefore, holes do not easily flow. Further, the resistance can be increased by doping the ZnSSe layer with a low concentration of N acceptor. Thereby, it can be made to work effectively as a current blocking layer.

The ZnSSe current blocking layer 7
2 is diffused during the second crystal growth step to obtain GaInP / AlGaInP.
The multiple quantum well active layer 70 is disordered. Therefore,
The optical waveguide structure and the window structure can be easily formed.

[0062]

As described above, according to the first aspect of the present invention, it is possible to reduce the leakage current that does not contribute to laser oscillation and to improve the external quantum efficiency of the laser. Can be provided.

According to the second aspect of the present invention, the stripe-shaped current confinement structure, the current confinement structure near the resonator end face, the optical waveguide structure, and the window structure can be formed by one pattern formation. It can be easily manufactured with a small number of steps.

According to the third aspect of the present invention, the superlattice structure of the active layer located below the current blocking layer is disordered, and the optical waveguide structure and the window structure are formed, so that the active layer is disordered. This eliminates the need for a diffusion step and an annealing step different from the crystal growth, and allows easy production with a smaller number of steps.

According to the fourth aspect of the present invention, since the crystal growth step only needs to be performed twice, the number of steps is small and the production can be further facilitated.

According to the fifth aspect of the present invention, the current blocking layer is made of a II-VI compound semiconductor containing Zn, so that the discontinuity of the band between the current blocking layer and the cladding layer is increased and the resistance is increased. Thus, an effective current confinement structure can be formed. In addition, Zn in the current blocking layer diffuses during the subsequent crystal growth step, and the superlattice structure of the active layer is disordered, so that the optical waveguide structure and the window structure can be easily formed.

[Brief description of the drawings]

1A and 1B are diagrams illustrating a semiconductor laser according to a first embodiment, wherein FIG. 1A is a perspective view of the semiconductor laser, FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. BB 'of (a)
It is a line sectional view.

2 (a) to 2 (e) are views showing a manufacturing process of the semiconductor laser shown in FIG. 1, and FIG. 2 (f) to FIG. FIG. 2 is a manufacturing process diagram viewed from a cross section taken along line BB ′ of FIG. 1.

3A and 3B are diagrams illustrating a semiconductor laser according to a second embodiment, wherein FIG. 3A is a perspective view of the semiconductor laser, FIG. 3B is a cross-sectional view taken along line AA ′ of FIG. 3A, and FIG. BB 'of (a)
It is a line sectional view.

4A to 4D are views showing the manufacturing process of the semiconductor laser of FIG. 3, in which FIG. 4A to FIG. FIG. 4 is a manufacturing process diagram viewed from a cross section taken along line BB ′ of FIG. 3.

5A and 5B are diagrams illustrating a semiconductor laser according to a third embodiment, wherein FIG. 5A is a perspective view of the semiconductor laser, FIG. 5B is a cross-sectional view taken along line AA ′ of FIG. BB 'of (a)
It is a line sectional view.

6A to 6C are diagrams showing a manufacturing process of the semiconductor laser of FIG. 5, wherein FIGS. 6A to 6C are manufacturing process diagrams viewed from a cross section taken along line AA 'of FIG. FIG. 6 is a manufacturing process diagram viewed from a cross section taken along line BB ′ of FIG. 5.

7A and 7B are diagrams illustrating a semiconductor laser according to a fourth embodiment, wherein FIG. 7A is a perspective view of the semiconductor laser, FIG. 7B is a cross-sectional view taken along line AA ′ of FIG. BB 'of (a)
It is a line sectional view.

FIG. 8 is a perspective view of a conventional semiconductor laser having a window structure.

FIG. 9 is a diagram showing the structure of another conventional semiconductor laser having a window structure, (a) is a perspective view of the semiconductor laser,
(B) is a sectional view taken along line AA 'of (a), and (c) is a sectional view taken along line BB' of (a).

[Explanation of symbols]

Reference Signs List 10 n-type GaAs substrate 12 n-type AlGaAs cladding layer 14 GaAs / AlGaAs multiple quantum well active layer 16 p-type AlGaAs cladding layer 18 p-type GaAs cap layer 20 n-type AlGaAs current blocking layer 22 p-type GaAs contact layer 24 p-side electrode 26 n-side electrode 28 AlGaAs mixed crystal 30 SiN mask 32 SiO ₂ layer 40 n-type AlGaInP cladding layer 42 GaInP active layer 44 p-type AlGaInP cladding layer 44 p-type GaInP band discontinuous relaxation layer 48 high concentration Zn-doped AlGaInP layer 50 n-type AlGaInP Current blocking layer 52 Zn diffusion region 60 p-type AlGaInP first cladding layer 61 groove 62 p-type AlGaInP second cladding layer 70 GaInP / AlGaInP multiple quantum well active layer 72 ZnS Se current block layer

Claims (5)

[Claims] 1. A lamination structure including at least a first conductivity type clad layer, an active layer including a superlattice structure, and a second conductivity type clad layer is formed on a first conductivity type semiconductor substrate, and a stripe-shaped region is formed. A current blocking layer made of a material having a larger forbidden band width than the active layer is formed on both outer sides and in the vicinity of the cavity end face, and the superlattice structure of the active layer located below the current blocking layer is disordered. A semiconductor laser. 2. A first conductive type semiconductor substrate, comprising at least a first conductive type clad layer, an active layer including a superlattice structure, a second conductive type clad layer, and a stripe-shaped structure of the second conductive type clad layer. A mesa stripe structure is formed by etching both sides of the region and the vicinity of the resonator end face, and a first material made of a material having a larger forbidden band width than the active layer embedded in both the outside of the mesa stripe structure and the vicinity of the resonator end face. Forming a stacked structure including a conductive type current block layer, a second conductive type cladding layer and a second conductive type contact layer formed on the first conductive type current blocking layer; A semiconductor laser, wherein the superlattice structure of the active layer located below the layer is disordered. 3. A first conductive type semiconductor substrate, comprising at least a first conductive type clad layer, an active layer having a superlattice structure, a second conductive type clad layer, and a striped shape of the second conductive type clad layer. A mesa stripe structure is formed by etching both outer sides of the region and the vicinity of the resonator end face, and a high mesa stripe made of a material having a larger forbidden band width than the active layer is formed on both outer sides of the mesa stripe structure and near the resonator end face. Density Z
An n-doping layer and a first conductivity type current blocking layer are buried, and a stacked structure including the second conductivity type cladding layer and a second conductivity type contact layer formed on the first conductivity type current blocking layer is formed. A semiconductor laser, wherein Zn is diffused and disordered in a superlattice structure of the active layer located under the high-concentration Zn-doped layer. 4. A semiconductor substrate having a first conductivity type, at least a cladding layer of a first conductivity type, an active layer having a superlattice structure, a first cladding layer of a second conductivity type, and a more forbidden band than the active layer. A high-concentration Zn-doped layer made of a wide material and a first-conductivity-type current blocking layer are stacked, and the high-concentration Zn-doping layer and the first-conductivity-type current blocking layer are etched in a stripe shape except for the vicinity of the cavity end face. A groove is formed, and a second second conductivity type clad layer is formed on the first second conductivity type clad layer and the first conductivity type current block layer exposed by the etching. A semiconductor laser, wherein Zn is diffused and disordered in a superlattice structure of the active layer located below a Zn doping layer. 5. The current blocking layer according to claim 1, wherein the current blocking layer contains Zn.
2. The semiconductor laser according to claim 1, comprising a Group VI compound semiconductor.